Flow Field Design Matters for High Current Density Zero-Gap CO2 Electrolyzers

Abstract

The commercialization of CO₂ electrolyzers requires higher current densities. This work demonstrates the necessity of flow field optimization for developing high-current-density CO₂ electrolyzers. Using three typical flow fields (serpentine, parallel, and interdigitated) as tools and combining multiple characterization techniques, we investigated the principles for further flow field optimization. We recognized that optimizing the flow field involves more than enhancing CO₂ distribution uniformity and ensuring no CO₂ starvation. It is also necessary to provide CO₂ flow-through transport while ensuring suppressed drainage behavior. Optimizing based on this principle, we fabricated a multiserpentine flow field, and it realized a high CO selectivity of about 95% at 0–350 mA cm^–2 with 0.1 M KHCO₃ and 50 °C cell temperature. Meanwhile, it achieves a high maximum CO partial current density of 409 mA cm^–2, which is 43.5% higher than that of the conventional parallel flow field.